A year ago, Ashlee Townsend, then 14, was running out of options. At 5 ft. 4 in., she weighed 330 lbs. and had developed Type 2 diabetes  a potentially life-threatening illness that usually doesn't occur before middle age. Ashlee had tried all sorts of diets, but none of them seemed to work. By third grade, she had so much difficulty walking that she started missing a lot of school. Then she underwent an operation that reduced her stomach from the size of a football to the size of an egg. In the 12 months since, she has lost 77 lbs.--in addition to the 40 lbs. she lost while preparing for surgery  and her diabetes is in remission. "The most amazing thing," says Ashlee, "is that I can see my feet when I walk."

Townsend is testing one of the most controversial weapons in the war against childhood obesity. Although the number is still small  doctors estimate that perhaps 150 U.S. teens have undergone so-called gastric-bypass surgery  it could jump dramatically. The percentage of children who are overweight and obese has tripled, from about 5% in 1980 to 15% in 2000, and a dozen hospitals around the U.S. either have started doing gastric bypasses on kids or are planning to. Dr. Thomas Inge of the Cincinnati Children's Hospital, where Ashlee had the surgery, estimates that as many as 250,000 American teens may be candidates for the operation.

That has a lot of physicians concerned. It's one thing for celebrities like TV weatherman Al Roker or singer Carnie Wilson to undergo gastric bypass. We are used to adults, even those who aren't famous, weighing the risks and benefits of such extreme treatments. But high school students? Can kids who have trouble planning for next week, let alone the rest of their lives, really understand what they are getting into?

Gastric bypass works by radically altering the size and shape of the stomach and shortening the length of the small intestine so that the body can no longer take in normal amounts of food. First, surgeons "staple" the stomach with surgical tools so that it can't hold more than about an ounce of food. Eat more than five or six bites, and you will feel a sense of nausea. Then the doctors rearrange the small intestine, the organ that actually absorbs nutrients, so that about a third of it can no longer function normally. Patients must take supplements for the rest of their life to avoid serious nutritional deficiencies. The procedure can, in theory, be reversed, though doing so would require complex surgery and the lost weight would probably be regained.

The bigger problem is that no one knows what this may do to someone who is still growing. Even under the best circumstances, there are substantial risks. As many as 1 in 100 obese adult patients dies from the procedure. A woman died in Massachusetts last month after the staples in her stomach apparently popped out. Blood clots and serious infections are also possible. In addition, 15% of patients regain the weight they lost. (By eating continually, you can stretch even the tiniest stomach.) In short, says Dr. David Ludwig, director of the obesity program at Children's Hospital, Boston, "you're substituting one potentially life-threatening condition for another."

On the other hand, it's hard not to sympathize with the plight of these youngsters. Many have suffered with obesity their entire life. "I just want to be able to go to a theme park and fit into any ride I want," says Paris Conley, 16, who is 5 ft. 7 in. and weighs 335 lbs.

"I would rather die on the operating table than go through life like this," Lauren Lebow remembers telling her mother. After surgery, the 5-ft. 3-in. Lebow shrank from 285 lbs. to 165 lbs.

Proponents of gastric bypass agree that it's not for everyone. "This is a treatment of last resort," says Inge. "The bar should be higher for adolescents than it is for adults." At Cincinnati Children's, that means prospective candidates must be at least 130 lbs. overweight  typical weights are 350 lbs. to 450 lbs.--or suffering from Type 2 diabetes or severe breathing problems. The cost of the operation runs from $25,000 to $40,000, and kids often miss a month of school during recovery. Patients must also participate in the hospital's nutrition, exercise and counseling programs. At Texas Children's Hospital in Houston, which has decided to launch a gastric-bypass program, patients must also agree to 10 years of follow-up visits.

Why the rush? critics ask. Dr. Diana Farmer, chief of pediatric surgery at the University of California San Francisco Children's Hospital, is among those who take a skeptical view. "Look, kids are not dropping dead at age 19 from obesity," she says. "Even in obese patients who have diabetes or sleep apnea, there are treatments." There is still time, Farmer and others insist, to work on losing weight the old-fashioned way through diet and exercise, which they concede is hard but not impossible. Then if folks are still obese when they reach adulthood, at least they are better prepared to decide whether to undergo such radical surgery.